The MPEG-4 Fine-Granular Scalability (FGS) framework allows for different levels of compression for different parts of an image by using an adaptive quantization technique, referred to as Selective Enhancement. Utilizing Selective Enhancement techniques, designated areas of an image may achieve a higher quality level than non-designated areas of the image. More specially, the enhancement data layers of designated areas of an image are transmitted with a higher priority than enhancement data layers of non-designated image areas. The higher priority of a designated area is achieved by “shifting” the bit-lane of an image element, such as a pixel array or a plurality of pixel arrays, i.e., a macroblock, to a higher priority level. Consequently, an enhancement factor or shift factor is associated to each array or macroblock.
A disadvantage of the current adaptive quantization method is that the shifting factors on the individual macroblocks are transmitted for each array or macroblock. This represents a significant overhead in transmission time and required bandwidth. The addition of enhancement or shifting factors consequently diminishes the image quality as the number of enhancement bits transmitted is reduced by the number of shifting factor bits transmitted.
Hence, there is a need to improve the efficiency of video data content bit transmission by reducing the number of non-video data content bits, such as enhancement factors transmitted.